The present disclosure relates to the field of tablet display technology, and particularly, to a pixel circuit and a driving method thereof, a display panel and a display device.
Organic Light Emitting Diode (OLED) display technology is an important development direction in current display technologies. The OLED display technology uses self-luminous organic light emitting diodes (OLEDs) to display images without the use of backlight elements. Compared with the Liquid Crystal Display (LCD) including the liquid crystal structure and the backlight element, it has the advantages of simple structure, thin thickness, and fast response. It is possible to satisfy the user's demand for a lighter, thinner, and more convenient display.
In the OLED display technology, the Active Matrix Organic Light Emitting Diode (AMOLED) technology and the Passive Matrix Organic Light Emitting Diode (PMOLED) technology are included according to the driving mode. PMOLED simply forms a matrix shape with cathode and anode, and lights up pixels in the array in a scanning way, and each pixel operates in a short pulse mode and emits light for instant high luminance. Its advantage is in the simple structure, which can effectively reduce the manufacturing cost. A potential problem is that the high drive voltage renders PMOLED not suitable for large-size and high-resolution panels. AMOLED technology uses a separate thin film transistor to control each pixel, which can be driven continuously and independently to emit light and can be driven using a low-temperature polysilicon or oxide TFT, and has advantages of low drive voltage and long life of the light emitting components. As a result, AMOLED technology has become the focus of the next generation of display technology.
FIG. 1 is a circuit diagram of an AMOLED pixel circuit disclosed in the prior art. As shown in FIG. 1, the pixel circuit uses drain current compensation transistors (a first transistor T1 and a seventh transistor T7) and threshold voltage compensation transistors (a fourth transistor T4 and an eighth transistor T8) to improve the flicker characteristics of the pixels and display an image with low flicker image quality.
However, the circuit in the prior art is still insufficient for the control precision of the OLED. As shown in FIG. 1, in the phase of writing data, the current flows from the drain to the source of the third transistor T3. In the light emission phase, the current flows from the source to the drain of the third transistor T3. Although the third transistor T3 has a symmetrical structure, the source and the drain can be exchanged for use. However, there is a slight difference between the drain-source voltage drop and the source-drain voltage drop of the third transistor T3, which will directly affect the control precision of the OLED and thus affect the precision of the OLED light emission. In addition, the circuit structure shown in FIG. 1 cannot eliminate the leakage current passing through the OLED outside the light emitting period, i.e., cannot eliminate the slight light emitting phenomenon caused by the leakage current.